Neither Baclofen nor Flexeril Should Be Used for Knee Contracture
Neither baclofen nor cyclobenzaprine (Flexeril) is appropriate for treating knee contracture, as both medications are indicated only for specific types of muscle dysfunction that do not include joint contractures from osteoarthritis or other rheumatic disorders. 1
Why These Medications Are Inappropriate
Baclofen Is Not Indicated
- Baclofen is FDA-approved exclusively for spasticity from upper motor neuron conditions (multiple sclerosis, spinal cord injury), not for peripheral musculoskeletal conditions 1
- The FDA label explicitly states: "Baclofen tablets are not indicated in the treatment of skeletal muscle spasm resulting from rheumatic disorders" 1
- There is only sparse evidence (2 trials) supporting baclofen for any musculoskeletal pain condition 2
- Baclofen works as a GABAB agonist for spasticity management, which is fundamentally different from the pathophysiology of joint contractures 2
Cyclobenzaprine Is Not Indicated
- Cyclobenzaprine is designed for acute muscle spasm from peripheral musculoskeletal conditions, not for chronic contractures 3
- All clinical trials of cyclobenzaprine were 2 weeks or less in duration, indicating it should only be used short-term for acute conditions 4
- The American Geriatrics Society advises avoiding cyclobenzaprine in older adults (who commonly have knee contractures) due to anticholinergic effects and sedation risk 5
- Cyclobenzaprine causes significant sedation through off-target histamine H1 receptor antagonism, with >30% of patients experiencing drowsiness 6
Appropriate Treatment for Knee Contracture
First-Line Non-Pharmacological Approaches
- Participate in cardiovascular and/or resistance land-based exercise programs 7
- Engage in aquatic exercise 7
- Lose weight if overweight (strongly recommended) 7
- Receive manual therapy in combination with supervised exercise 7
- Use walking aids as needed 7
- Apply medially directed patellar taping 7
Pharmacological Management for Pain (Not Contracture Itself)
- Start with acetaminophen up to 4,000 mg/day as the first-line oral analgesic 7
- Progress to topical NSAIDs (especially for patients ≥75 years) or oral NSAIDs if acetaminophen fails 7
- Consider intra-articular corticosteroid injections for flare of knee pain, especially with effusion 7
- Tramadol may be used as an alternative if NSAIDs are contraindicated 7
Important Caveats
- Contractures represent fixed structural changes in soft tissue and joint capsule that require physical interventions (stretching, range of motion, serial casting) rather than muscle relaxants 2
- If the contracture is causing spasticity-related pain from an upper motor neuron condition (stroke, cerebral palsy), then baclofen might be considered, but this is a different clinical scenario than simple knee contracture 2, 1
- For focal spasticity affecting a joint post-stroke, botulinum toxin is strongly preferred over oral baclofen 2